1. Field of the Invention
The present invention relates to a shift lever device using a magnetism detection switch which uses a magnetoresistive device to enable detection of three detection positions.
2. Description of the Related Art
Japanese Unexamined Patent Application Publication No. 2007-273528 and Japanese Unexamined Patent Application Publication No. 2007-220367 disclose a magnetism detection switch using a magnetoresistive device.
The switch described in Japanese Unexamined Patent Application Publication No. 2007-273528 includes a magnetism sensor using a magnetoresistive device and two magnets, which move relative to each other. The two magnets are arrayed with different magnetic poles facing the magnetism sensor. The magnetism sensor moves between a first position facing one of the magnets, and a second position facing the other of the magnets.
The magnetoresistive device has a pinned magnetic layer pinned in a direction orthogonal to the direction in which the two magnets are arrayed. The direction of magnetism of a free magnetic layer changes between the first position and second position, and as a result, the detection output of the magnetism sensor is switched between on and off.
The switch described in Japanese Unexamined Patent Application Publication No. 2007-220367 has two gaps between yokes, and the orientation of the magnetic fields within each of the gaps is 180 degrees opposite. A magnetoresistive device is mounted on a tip portion of a sliding mechanism. This magnetoresistive device passes through the two gaps, with different switching output being obtained depending on whether situated within one gap or in the other.
The magnetism detection switches described in Japanese Unexamined Patent Application Publication No. 2007-273528 and Japanese Unexamined Patent Application Publication No. 2007-220367 use magnetoresistive devices, so switching output can be obtained without contact. However, both switches are only capable of detecting two positions, and cannot obtain detection output distinguishing three detection positions.
Next, Japanese Unexamined Patent Application Publication No. 2008-32155 and Japanese Unexamined Patent Application Publication No. 2007-333490 disclose a shift lever device of an automobile transmission using a non-contact detecting mechanism.
The shift lever device described in Japanese Unexamined Patent Application Publication No. 2008-32155 includes a position sensor with Hall elements configured at each of multiple switching positions. Tilting a shift lever moves a magnet. The magnet moves through the detection areas of each of the multiple position sensors, and thus multi-stage switching detection output is obtained.
The shift lever device described in Japanese Unexamined Patent Application Publication No. 2007-333490 includes multiple bias magnets and a magnetoresistive device fixed at a fixed portion, and a counter magnet is moved by a shift lever. The magnetic field is drawn into the counter magnet from the bias magnets, so the orientation of the magnetic field applied to the magnetoresistive device changes in accordance with the position to which the counter magnet has moved. Detecting the orientation of the magnetic field by the magnetoresistive device enables detection of which switching position the counter magnet has moved to.
The shift lever device described in Japanese Unexamined Patent Application Publication No. 2008-32155 necessitates a great number of position sensors to be provided, so the structure is complicated. Also, the shift lever device described in Japanese Unexamined Patent Application Publication No. 2007-333490 detects the orientation of the magnetic field applied to the magnetoresistive device, so there is the possibility of erroneous detection, and highly-reliable output is not easily obtained.